CA2247495C - Chemically induced stimulation of cleat formation in a subterranean coal formation - Google Patents
Chemically induced stimulation of cleat formation in a subterranean coal formation Download PDFInfo
- Publication number
- CA2247495C CA2247495C CA002247495A CA2247495A CA2247495C CA 2247495 C CA2247495 C CA 2247495C CA 002247495 A CA002247495 A CA 002247495A CA 2247495 A CA2247495 A CA 2247495A CA 2247495 C CA2247495 C CA 2247495C
- Authority
- CA
- Canada
- Prior art keywords
- formation
- well
- methane
- oxidant solution
- production
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 230000015572 biosynthetic process Effects 0.000 title claims abstract description 116
- 239000003245 coal Substances 0.000 title claims abstract description 74
- 230000000638 stimulation Effects 0.000 title description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 86
- 239000007800 oxidant agent Substances 0.000 claims abstract description 50
- 230000001590 oxidative effect Effects 0.000 claims abstract description 48
- 238000004519 manufacturing process Methods 0.000 claims abstract description 44
- 238000000034 method Methods 0.000 claims abstract description 27
- XTEGARKTQYYJKE-UHFFFAOYSA-M Chlorate Chemical class [O-]Cl(=O)=O XTEGARKTQYYJKE-UHFFFAOYSA-M 0.000 claims abstract description 14
- -1 perborate Chemical class 0.000 claims abstract description 12
- 150000003839 salts Chemical class 0.000 claims abstract description 12
- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 claims abstract description 10
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical class OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 claims abstract description 8
- JRKICGRDRMAZLK-UHFFFAOYSA-L peroxydisulfate Chemical class [O-]S(=O)(=O)OOS([O-])(=O)=O JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 claims abstract description 8
- 229910002651 NO3 Inorganic materials 0.000 claims abstract description 7
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical class [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims abstract description 7
- VLTRZXGMWDSKGL-UHFFFAOYSA-M perchlorate Inorganic materials [O-]Cl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-M 0.000 claims abstract description 7
- MWNQXXOSWHCCOZ-UHFFFAOYSA-L sodium;oxido carbonate Chemical class [Na+].[O-]OC([O-])=O MWNQXXOSWHCCOZ-UHFFFAOYSA-L 0.000 claims abstract description 7
- 239000004155 Chlorine dioxide Substances 0.000 claims abstract description 5
- 235000019398 chlorine dioxide Nutrition 0.000 claims abstract description 5
- 239000000243 solution Substances 0.000 claims description 37
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 25
- 238000002347 injection Methods 0.000 claims description 24
- 239000007924 injection Substances 0.000 claims description 24
- 239000012530 fluid Substances 0.000 claims description 11
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical class C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 4
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- 229910052708 sodium Inorganic materials 0.000 claims description 4
- 239000011734 sodium Substances 0.000 claims description 4
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical class [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims 2
- 229910052700 potassium Chemical class 0.000 claims 2
- 239000011591 potassium Chemical class 0.000 claims 2
- 239000007864 aqueous solution Substances 0.000 claims 1
- 150000002823 nitrates Chemical class 0.000 claims 1
- 230000004936 stimulating effect Effects 0.000 abstract description 2
- 238000005755 formation reaction Methods 0.000 description 93
- 230000035699 permeability Effects 0.000 description 10
- 239000007789 gas Substances 0.000 description 9
- 238000011084 recovery Methods 0.000 description 8
- 238000010586 diagram Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000000149 penetrating effect Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000011282 treatment Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 229910052736 halogen Inorganic materials 0.000 description 2
- 150000002367 halogens Chemical class 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 159000000001 potassium salts Chemical class 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000008398 formation water Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 230000003362 replicative effect Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 238000010517 secondary reaction Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
- C09K8/66—Compositions based on water or polar solvents
- C09K8/665—Compositions based on water or polar solvents containing inorganic compounds
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/84—Compositions based on water or polar solvents
- C09K8/845—Compositions based on water or polar solvents containing inorganic compounds
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/006—Production of coal-bed methane
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/17—Interconnecting two or more wells by fracturing or otherwise attacking the formation
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/27—Methods for stimulating production by forming crevices or fractures by use of eroding chemicals, e.g. acids
Abstract
A method for increasing the production of methane from a subterranean coal formation by chemically stimulating the formation of cleats in the formation to increase the rate of methane production from the formation by injecting an aqueous oxidant solution into the formation to stimulate the formation of cleats in the formation; and thereafter producing methane from the formation at an increased rate. Suitable oxidants include chlorine dioxide, metallic salts of perchlorate, chlorate, persulfate, perborate, percarbonate, permanganate, nitrate and combinations thereof.
Description
CHEMICALLY INDUCED STIMULATION OF CLEAT FORMATION
IN A SUBTERRANEAN COAL FORMATION
This invention relates to methods for increasing the rate of production of methane from a subterranean coal formation by chemically stimulating the formation with an aqueous oxidizing solution to increase the production rate of methane from the formation.
Brief Description of the Prior Art Substantial quantities of methane gas are found in subterranean coal formations. A variety of processes have been used in attempts to recover the methane from such coal formations more efficientlY.
The simplest process is the pressure reduction process wherein a borehole is drilled into a coal formation from the surface and methane is withdrawn from the borehole by reducing the pressure to cause methane to be desorbed from and flow from the coal formation into the borehole and to the surface. This method is not . . , efficient because coal formations are generally not extremely porous and the majority of the methane is generally not found in the pores of the coal formation but is absorbed or adsorbed to the coal. While methane can be produced from coal formations by this process, the production of inethane is relatively slow.
In some coal formations, the natural permeability is sufficient to allow the removal of in situ water to permit the enhanced recovery of methane. In such formations, cleat systems developed during the coal bed diagenesis provide channel ways through which water and methane migrate to the production wells for removal.
This removal of water or "de-watering" of the coal formations removes water from the channel ways and permits the flow of - taethane through the channel ways and to a production well at a greater rate. -Many coal formations do not have extensively developed cleat systems or have cleat systems which are not fully developed. These coal formations have very low permeability to water and gas and do not yield water or gas at significant rates. As a result, the water fills the channels, and the recovery of methane from such coal formations is difficult or impossible at significant rates. Such low permeability water-containing coal formations may be either water saturated or less than fully water saturated. It appears that coal formations with better developed cleat systems may have been exposed to a diffusive oxidizing fluid of some type during the geologic past whereas coal formations with less developed cleat systems do not show evidence of exposure to an oxidizing fluid in the past.
The terms "absorbed" and "adsorbed" are used interchangeably in the discussion herein to refer to methane or other light hydrocarbons which are retained in or on the surfaces of carbonaceous or other materials.
Accordingly, continuing efforts have been directed to the development of methods for replicating the effects of the conditions in the better developed cleat system coal formations and increasing the production rate of inethane from such formations.
In our GB-A-2309719, we describe a method of increasing the rate of production of methane from a subterranean coal formation which comprises injecting an aqueous oxidant solution into the formation and maintaining the solution in the formation for a time sufficient to stimulate the formation of cleats in the formation. Hydrogen peroxide, ozone and oxygen are specifically mentioned as suitable oxidants. In subsequent experiments using metal salts and certain halogen-containing compounds as oxidants, however, we found that the treatment sometimes causes unexpected and undesired side effects such as secondary reactions with components of the formation leading to clogging of the cleats and therefore a less than optimum improvement in methane recovery. Moreover, it cannot be predicted which metal salts or halogen-containing compounds will be associated with these undesirable side effects.
As a result of further extensive experimentation, however, we have now found that these side effects can be minimised or avoided if the oxidant is selected from at least one member of the group consisting of chlorine dioxide and water soluble metal salts of perchlorate, chlorate, persulfate, perborate, percarbonate, permanganate and nitrate.
According to the present invention, there is provided a method of increasing the rate of production of methane from a subterranean coal formation penetrated by at least one well by injecting an aqueous oxidant solution into the formation, maintaining the aqueous oxidant solution in the formation for a selected time to stimulate the formation of cleats in the formation, and producing methane from the formation at an increased rate, characterised in that said oxidant solution contains at least one oxidant selected from the group consisting of chlorine dioxide, water soluble metallic salts of perchlorate, perborate, chlorate, persulfate, percarbonate, permanganate, and nitrate, and combinations thereof.
In accordance with one embodiment of the invention, the rate of production of methane from a subterranean coal formation penetrated by at least one injection well and at least one production well is increased by:
a) injecting the aqueous oxidant solution into the formation through the injection well; and b) producing methane from the formation through the production well at an increased rate.
The present invention, which is effective to enhance methane recovery from coal formations, will now be described in greater detail with reference to preferred embodiments to thereof.and with the aid of the accompanying drawings in which:
FIG 1 is a schematic diagram of a formed well penetrating a subterranean coal formation from the surface, wherein the inventive method as described may be employed.
FIG 2 is a schematic diagram of a formed well penetrating a subterranean coal formation from the surface, wherein the coal formation has been fractured and wherein the inventive method as described may be employed.
FIG 3 is a schematic diagram of a formed injection well and production well penetrating a subterranean coal formation from the surface, wherein the inventive method as described may be employed.
FIG 4 is a schematic diagram of a formed injection well and a production well penetrating a subterranean coal formation from the surface, wherein the coal formation has been fractured from the injection well and wherein the inventive method as described may be employed.
IN A SUBTERRANEAN COAL FORMATION
This invention relates to methods for increasing the rate of production of methane from a subterranean coal formation by chemically stimulating the formation with an aqueous oxidizing solution to increase the production rate of methane from the formation.
Brief Description of the Prior Art Substantial quantities of methane gas are found in subterranean coal formations. A variety of processes have been used in attempts to recover the methane from such coal formations more efficientlY.
The simplest process is the pressure reduction process wherein a borehole is drilled into a coal formation from the surface and methane is withdrawn from the borehole by reducing the pressure to cause methane to be desorbed from and flow from the coal formation into the borehole and to the surface. This method is not . . , efficient because coal formations are generally not extremely porous and the majority of the methane is generally not found in the pores of the coal formation but is absorbed or adsorbed to the coal. While methane can be produced from coal formations by this process, the production of inethane is relatively slow.
In some coal formations, the natural permeability is sufficient to allow the removal of in situ water to permit the enhanced recovery of methane. In such formations, cleat systems developed during the coal bed diagenesis provide channel ways through which water and methane migrate to the production wells for removal.
This removal of water or "de-watering" of the coal formations removes water from the channel ways and permits the flow of - taethane through the channel ways and to a production well at a greater rate. -Many coal formations do not have extensively developed cleat systems or have cleat systems which are not fully developed. These coal formations have very low permeability to water and gas and do not yield water or gas at significant rates. As a result, the water fills the channels, and the recovery of methane from such coal formations is difficult or impossible at significant rates. Such low permeability water-containing coal formations may be either water saturated or less than fully water saturated. It appears that coal formations with better developed cleat systems may have been exposed to a diffusive oxidizing fluid of some type during the geologic past whereas coal formations with less developed cleat systems do not show evidence of exposure to an oxidizing fluid in the past.
The terms "absorbed" and "adsorbed" are used interchangeably in the discussion herein to refer to methane or other light hydrocarbons which are retained in or on the surfaces of carbonaceous or other materials.
Accordingly, continuing efforts have been directed to the development of methods for replicating the effects of the conditions in the better developed cleat system coal formations and increasing the production rate of inethane from such formations.
In our GB-A-2309719, we describe a method of increasing the rate of production of methane from a subterranean coal formation which comprises injecting an aqueous oxidant solution into the formation and maintaining the solution in the formation for a time sufficient to stimulate the formation of cleats in the formation. Hydrogen peroxide, ozone and oxygen are specifically mentioned as suitable oxidants. In subsequent experiments using metal salts and certain halogen-containing compounds as oxidants, however, we found that the treatment sometimes causes unexpected and undesired side effects such as secondary reactions with components of the formation leading to clogging of the cleats and therefore a less than optimum improvement in methane recovery. Moreover, it cannot be predicted which metal salts or halogen-containing compounds will be associated with these undesirable side effects.
As a result of further extensive experimentation, however, we have now found that these side effects can be minimised or avoided if the oxidant is selected from at least one member of the group consisting of chlorine dioxide and water soluble metal salts of perchlorate, chlorate, persulfate, perborate, percarbonate, permanganate and nitrate.
According to the present invention, there is provided a method of increasing the rate of production of methane from a subterranean coal formation penetrated by at least one well by injecting an aqueous oxidant solution into the formation, maintaining the aqueous oxidant solution in the formation for a selected time to stimulate the formation of cleats in the formation, and producing methane from the formation at an increased rate, characterised in that said oxidant solution contains at least one oxidant selected from the group consisting of chlorine dioxide, water soluble metallic salts of perchlorate, perborate, chlorate, persulfate, percarbonate, permanganate, and nitrate, and combinations thereof.
In accordance with one embodiment of the invention, the rate of production of methane from a subterranean coal formation penetrated by at least one injection well and at least one production well is increased by:
a) injecting the aqueous oxidant solution into the formation through the injection well; and b) producing methane from the formation through the production well at an increased rate.
The present invention, which is effective to enhance methane recovery from coal formations, will now be described in greater detail with reference to preferred embodiments to thereof.and with the aid of the accompanying drawings in which:
FIG 1 is a schematic diagram of a formed well penetrating a subterranean coal formation from the surface, wherein the inventive method as described may be employed.
FIG 2 is a schematic diagram of a formed well penetrating a subterranean coal formation from the surface, wherein the coal formation has been fractured and wherein the inventive method as described may be employed.
FIG 3 is a schematic diagram of a formed injection well and production well penetrating a subterranean coal formation from the surface, wherein the inventive method as described may be employed.
FIG 4 is a schematic diagram of a formed injection well and a production well penetrating a subterranean coal formation from the surface, wherein the coal formation has been fractured from the injection well and wherein the inventive method as described may be employed.
FIG. 5 is a schematic layout of a 5-spot injection and production well pattem.
Description of Preferred Embodiments In the discussion of the Figures, the same numbers will be used throughout the specification to refer to the same or sinmidar components, In Fig. 1, a coal formation 10-penetrated from a surface 12 by a wellbore 14 is shown. The wellbore 14 includes a casing 16 positioned in the wellbore 14 by cement 18. While wellbore 14 is shown as -a cased wellbore it should be understood that in the preferred embodiments shown in the Figures, cased or uncased wellbores could be used. Alternatively, the casing 16 could extend into or through the coal formation 10 with perforations through the casing in the coal seam providing fluid communication with the coal formation from the wellbore 14. The wellbore 14 extends into the coal formation 10 and includes a tubing 20 and a packer 22.
The packer 22 is positioned to prevent flow between the outer diameter of the tubing 20 and the inner diameter of the casing 16. The wellbore 14 also includes equipment 24 adapted to inject a gaseous or_liquid stream into the coal formation 10 or to recover a gaseous .or liquid stream from the coal formation 10. -In the practice of the present invention, the aqueous oxidant solution is injected as shown by an arrow 26 through the tubing 20 into the coal formation 10 as shown by arrows 28. The zones treated are shown by circles 30., The aqueous oxidant solution is injected into the coal formation 10 for a selected time to enhance or stimulate the formation of a conductive, contiguous cleat system in the coal formation 10. The aqueous oxidant solution is injected for a period of time and in a quantity considered sufficient to- increase the permeability of the coal formation 10 in the zones 30. After a selected period or after a selected amount of the aqueous oxidant solution has been injected, the well is shut in for a period of time which may be up to or greater than 24 hours. Typically, the well is shut-in until the pressure in the wellbore retusns to the formation pressure amd thereafter for at least 12 additional hours.
Alternatively, a sufficient period of oxidant solution presence in the coal formation may have elapsed during the injection of the aqueous oxidant solution. The shut-in period allows for migration of the oxidant solution into the coal formation 10 to oxidize components of the coal formation 10 to enhance the cleat system in the coal formation 10. Subsequent to the shut-in period, water, methane or both may be recovered from the coal formation 10 to de-water the coal formation in the zones 30 and produce methane. The term. "de-water" as used herein does not refer to the complete removal of ovater from the coal formation 10, but rather to the removal of sufficient water from the coal formation 10 to open passage ways in the cleat system in coal formation 10 so that methane can be produced through the passage ways from the coal formation 10.
The aqueous oxidant solution contains an oxidant selected from the group consisting of at least one of chlorine dioxide and water-soluble metallic salts of perchlorate, chlorate, persulfate, perborate, percarbonate, permanganate, nitrate and combinations thereof. Preferred are the water soluble metallic salts of perchlorate, persulfate, perborate, chlorate, percarbonate, permanganate, nitrate and combinations thereof; of these the sodium and potassium salts of perchlorate, chlorate, persulfate, perborate,_ percarbonate, permanganate, nitrate and combinations thereof are particularly preferred. Typically, the oxidant is 'used in concentrations up to the solubility limit of the oxidant in the aqueous oxidant solution.
Preferred met.allic salts are sodium and potassium salts. Such oxidants have been used as a fracturing fluid gel breaker in hydrocarbon-bearing formation fracturing applications and are commercially available.
In the embodiment shown in Fig. 1, a single well is used for injection of the aqueous oxidant solution to chemically enhance or stimulate the formation of a cleat system in the zones 30 to result in the release of formation water and an increase in -~~-the methane production rate from the coal formation 10. The term "increase" as used herein refers to a change relative to. the untreated coal formation.
In Fig. 2, a similar embodiment is shown except that the coal formation 10 has been fractured by fractures 32. The operation of the well is basically the same as that shown in Fig. 1 except that the coal formation 10 has previously been fractured or is fractured by a fluid which may comprise the aqueous oxidant solution during at least part of the fracturing operation. For instance, it may be desirable to use a conventional fracturing application, 'if - the. coal formation 10 is sufficiently impermeable, as an initial stimulation method folIowed by the aqueous oxidant solution as a post=fracturing flush. The post-fracturing flush enhances cleat permeability throughout the areas contacting the fracture. In such instances, the well is desirably shut-in as discussed previously -and the oxidants are selected from the same oxidant materials discussed previously. The fractures are formed in the coal formation 10 prior to injection of the oxidant solution. The oxidant solution could comprise the fracturing fluid if desired. The aqueous oxidant solution could also be injected above or below the fracture gradient (pressure) if desired.
In Fig. 3, an injection well 34 and production well 36 penetrate the coal formation 10 from the surface 12. The injection well 34 is spaced apart from the production well 36 at a spacing based upon the characteristics of the particular coal formation and the like. According to the present invention, the aqueous oxidant solution described above is injected into the coal formation 10 through the injection well 34 as shown by the arrow 26 and the arrows 28 to treat the zones 30 which may extend from the injection well 34 in a generally circumferential direction, but generally extend preferentially toward a nearby production well 36 or production wells. The production well 36 is positioned to withdraw water and methane from the coal formation 10. The production of water and methane through the production well 36 causes the aqueous oxidant solution to migrate toward the production well 36.
Desirably, injection of the aqueous oxidant solution is continued until an increased water volume is detected in productiou well 36 or until a desired increase in permeability or an increase in the volume of fluids produced is achieved. The increase in the permeability or volume of flilids produced from the production well 36 is indicative of the formation or enhancement of cleats in the coal formation 10 with a resulting increase in permeability so that additional quantities of fluids are released from the coal formation 10 for production as shown by arrows 38 through the production well 36 and a line 40. The arrows 38 are shown directed toward the production well 36 from both directions in contemplation that water will continue to be recovered at a lower rate from untreated portions of the coal formation 10.
The embodiment shown in Fig. 4 is similar to that shown in Fig. 3 except that the coal formation 10 has been fractured by fractures 32. Fractures 32 in the embodiment shown in Fig. 2 can be of substantially any extent. By contrast, in the embodiment shown in Fig. 4, the fractures 32 desirably extend no more than half way to the production well 36. Clearly, if the fractures 32 extend completely into the production well 36, it will be difficult to use any kind of fluid or gas drive between injection well 34 and production well 36. Desirably, the fractures extend no more than half the distance between the injection well 34 and the production well 36. The use of the aqueous oxidant solution with the fractures 32 is as discussed previously.
In Fig. 5, a 5-spot well arrangement is shown. Nlultiple well arrangements, such as 5-spot well arrangements, are useful in the practice of the present invention and may be used in a recurring pattern over a wide area. Such arrangements are well known to those skilled in the art and will be 'discussed only briefly. In the arrangement shown in Fig. 5, the aqueous oxidant solution is injected through the injection well 34 to treat the zones 30 to enhance the recovery of water and methane from the production wells 36. When the desired cleat formation or permeability increase has been achieved as evidenced by the production of fluids at an increased rate from production well 36, the injection of the aqueous oxidant solution is stopped and the injection well 34 can be converted to a production well. The area would then be produced through the original production wells and the converted injection well.
_ 7 The areas of enhanced cleat formation will increase the methane production rates and the ultimate methane recovery.
The method of the present invention is also useful as a pre-treatment for gas injection treatments to enhance the recovery of methane from the coal formation 10.
The use of carbon dioxide, either alone or with other gases, to increase the production of methane from coal formations is well known. Similarly, the use of inert gases, such as nitrogen, argon and the like, to remove additional quantities of methane from coal formations by increasing the pres=e in the formation and thereby removing additional methane as the methane partial pressure in the atmosphere in the coal seam is decreased are well known to those skilled in the art. The use of such processes requires that the formation be permeable to gas flow into or through the formation so that the methane can be recovered. The method of the present invention enhances the permeability of coal formations and may be used prior to the use of gas sweep or gas desorption treatments to enhance the recovery of methane.
Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments discussed are illustrative rather than limiting in nature and that many variations and modifications are possible within the scope of the present invention. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments.
-- - ------- --- --- --------
Description of Preferred Embodiments In the discussion of the Figures, the same numbers will be used throughout the specification to refer to the same or sinmidar components, In Fig. 1, a coal formation 10-penetrated from a surface 12 by a wellbore 14 is shown. The wellbore 14 includes a casing 16 positioned in the wellbore 14 by cement 18. While wellbore 14 is shown as -a cased wellbore it should be understood that in the preferred embodiments shown in the Figures, cased or uncased wellbores could be used. Alternatively, the casing 16 could extend into or through the coal formation 10 with perforations through the casing in the coal seam providing fluid communication with the coal formation from the wellbore 14. The wellbore 14 extends into the coal formation 10 and includes a tubing 20 and a packer 22.
The packer 22 is positioned to prevent flow between the outer diameter of the tubing 20 and the inner diameter of the casing 16. The wellbore 14 also includes equipment 24 adapted to inject a gaseous or_liquid stream into the coal formation 10 or to recover a gaseous .or liquid stream from the coal formation 10. -In the practice of the present invention, the aqueous oxidant solution is injected as shown by an arrow 26 through the tubing 20 into the coal formation 10 as shown by arrows 28. The zones treated are shown by circles 30., The aqueous oxidant solution is injected into the coal formation 10 for a selected time to enhance or stimulate the formation of a conductive, contiguous cleat system in the coal formation 10. The aqueous oxidant solution is injected for a period of time and in a quantity considered sufficient to- increase the permeability of the coal formation 10 in the zones 30. After a selected period or after a selected amount of the aqueous oxidant solution has been injected, the well is shut in for a period of time which may be up to or greater than 24 hours. Typically, the well is shut-in until the pressure in the wellbore retusns to the formation pressure amd thereafter for at least 12 additional hours.
Alternatively, a sufficient period of oxidant solution presence in the coal formation may have elapsed during the injection of the aqueous oxidant solution. The shut-in period allows for migration of the oxidant solution into the coal formation 10 to oxidize components of the coal formation 10 to enhance the cleat system in the coal formation 10. Subsequent to the shut-in period, water, methane or both may be recovered from the coal formation 10 to de-water the coal formation in the zones 30 and produce methane. The term. "de-water" as used herein does not refer to the complete removal of ovater from the coal formation 10, but rather to the removal of sufficient water from the coal formation 10 to open passage ways in the cleat system in coal formation 10 so that methane can be produced through the passage ways from the coal formation 10.
The aqueous oxidant solution contains an oxidant selected from the group consisting of at least one of chlorine dioxide and water-soluble metallic salts of perchlorate, chlorate, persulfate, perborate, percarbonate, permanganate, nitrate and combinations thereof. Preferred are the water soluble metallic salts of perchlorate, persulfate, perborate, chlorate, percarbonate, permanganate, nitrate and combinations thereof; of these the sodium and potassium salts of perchlorate, chlorate, persulfate, perborate,_ percarbonate, permanganate, nitrate and combinations thereof are particularly preferred. Typically, the oxidant is 'used in concentrations up to the solubility limit of the oxidant in the aqueous oxidant solution.
Preferred met.allic salts are sodium and potassium salts. Such oxidants have been used as a fracturing fluid gel breaker in hydrocarbon-bearing formation fracturing applications and are commercially available.
In the embodiment shown in Fig. 1, a single well is used for injection of the aqueous oxidant solution to chemically enhance or stimulate the formation of a cleat system in the zones 30 to result in the release of formation water and an increase in -~~-the methane production rate from the coal formation 10. The term "increase" as used herein refers to a change relative to. the untreated coal formation.
In Fig. 2, a similar embodiment is shown except that the coal formation 10 has been fractured by fractures 32. The operation of the well is basically the same as that shown in Fig. 1 except that the coal formation 10 has previously been fractured or is fractured by a fluid which may comprise the aqueous oxidant solution during at least part of the fracturing operation. For instance, it may be desirable to use a conventional fracturing application, 'if - the. coal formation 10 is sufficiently impermeable, as an initial stimulation method folIowed by the aqueous oxidant solution as a post=fracturing flush. The post-fracturing flush enhances cleat permeability throughout the areas contacting the fracture. In such instances, the well is desirably shut-in as discussed previously -and the oxidants are selected from the same oxidant materials discussed previously. The fractures are formed in the coal formation 10 prior to injection of the oxidant solution. The oxidant solution could comprise the fracturing fluid if desired. The aqueous oxidant solution could also be injected above or below the fracture gradient (pressure) if desired.
In Fig. 3, an injection well 34 and production well 36 penetrate the coal formation 10 from the surface 12. The injection well 34 is spaced apart from the production well 36 at a spacing based upon the characteristics of the particular coal formation and the like. According to the present invention, the aqueous oxidant solution described above is injected into the coal formation 10 through the injection well 34 as shown by the arrow 26 and the arrows 28 to treat the zones 30 which may extend from the injection well 34 in a generally circumferential direction, but generally extend preferentially toward a nearby production well 36 or production wells. The production well 36 is positioned to withdraw water and methane from the coal formation 10. The production of water and methane through the production well 36 causes the aqueous oxidant solution to migrate toward the production well 36.
Desirably, injection of the aqueous oxidant solution is continued until an increased water volume is detected in productiou well 36 or until a desired increase in permeability or an increase in the volume of fluids produced is achieved. The increase in the permeability or volume of flilids produced from the production well 36 is indicative of the formation or enhancement of cleats in the coal formation 10 with a resulting increase in permeability so that additional quantities of fluids are released from the coal formation 10 for production as shown by arrows 38 through the production well 36 and a line 40. The arrows 38 are shown directed toward the production well 36 from both directions in contemplation that water will continue to be recovered at a lower rate from untreated portions of the coal formation 10.
The embodiment shown in Fig. 4 is similar to that shown in Fig. 3 except that the coal formation 10 has been fractured by fractures 32. Fractures 32 in the embodiment shown in Fig. 2 can be of substantially any extent. By contrast, in the embodiment shown in Fig. 4, the fractures 32 desirably extend no more than half way to the production well 36. Clearly, if the fractures 32 extend completely into the production well 36, it will be difficult to use any kind of fluid or gas drive between injection well 34 and production well 36. Desirably, the fractures extend no more than half the distance between the injection well 34 and the production well 36. The use of the aqueous oxidant solution with the fractures 32 is as discussed previously.
In Fig. 5, a 5-spot well arrangement is shown. Nlultiple well arrangements, such as 5-spot well arrangements, are useful in the practice of the present invention and may be used in a recurring pattern over a wide area. Such arrangements are well known to those skilled in the art and will be 'discussed only briefly. In the arrangement shown in Fig. 5, the aqueous oxidant solution is injected through the injection well 34 to treat the zones 30 to enhance the recovery of water and methane from the production wells 36. When the desired cleat formation or permeability increase has been achieved as evidenced by the production of fluids at an increased rate from production well 36, the injection of the aqueous oxidant solution is stopped and the injection well 34 can be converted to a production well. The area would then be produced through the original production wells and the converted injection well.
_ 7 The areas of enhanced cleat formation will increase the methane production rates and the ultimate methane recovery.
The method of the present invention is also useful as a pre-treatment for gas injection treatments to enhance the recovery of methane from the coal formation 10.
The use of carbon dioxide, either alone or with other gases, to increase the production of methane from coal formations is well known. Similarly, the use of inert gases, such as nitrogen, argon and the like, to remove additional quantities of methane from coal formations by increasing the pres=e in the formation and thereby removing additional methane as the methane partial pressure in the atmosphere in the coal seam is decreased are well known to those skilled in the art. The use of such processes requires that the formation be permeable to gas flow into or through the formation so that the methane can be recovered. The method of the present invention enhances the permeability of coal formations and may be used prior to the use of gas sweep or gas desorption treatments to enhance the recovery of methane.
Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments discussed are illustrative rather than limiting in nature and that many variations and modifications are possible within the scope of the present invention. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments.
-- - ------- --- --- --------
Claims (9)
1. A method of increasing the rate of production of methane from a subterranean coal formation penetrated by at least one well by injecting an aqueous oxidant solution into the formation, maintaining the aqueous oxidant solution in the formation for a selected time to stimulate the formation of cleats in the formation, and producing methane from the formation at an increased rate, characterised in that said oxidant solution contains at least one oxidant selected from the group consisting of chlorine dioxide, water soluble metallic salts of perchlorate, perborate, chlorate, persulfate, percarbonate, permanganate, and nitrate, and combinations thereof.
2. A method as claimed in Claim 1 wherein the water soluble metal salts are salts of sodium or potassium.
3. A method as claimed in Claim 2 wherein the aqueous oxidant solution comprises an aqueous solution of at least one salt selected from perchlorates, persulfates, perborates, percarbonates, permanganates and nitrates of sodium and potassium.
4. A method as claimed in Claim 1, Claim 2 or Claim 3 wherein the aqueous oxidant solution is injected into the formation through a first well, the first well is shut-in for a selected time, and thereafter methane is produced from the first well at an increased rate.
5. A method as claimed in any one of claims 1 through 4, wherein the formation has been fractured with fractures extending from the well prior to injection of the aqueous oxidant solution.
6. A method as claimed in any one of claims 1 through 5, wherein the aqueous oxidant solution comprises a fracturing fluid injected at fracturing conditions to fracture the formation.
7. A method as claimed in any one of claims 1 through 6, wherein said aqueous oxidant solution is maintained in the formation for at least 24 hours.
8. A method as claimed in any one of claims 1 through 7, wherein the oxidant is present in an amount up to the solubility limit of the oxidant in water.
9. A method as claimed in any one of claims 1 through 7 for increasing the production of methane from a subterranean coal formation penetrated by at least one injection well and at least one production well, the method comprising:
a) injecting the aqueous oxidant solution into the formation through the injection well; and b) producing methane from the formation through the production well at an increased rate.
a) injecting the aqueous oxidant solution into the formation through the injection well; and b) producing methane from the formation through the production well at an increased rate.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US08/934,722 US5964290A (en) | 1996-01-31 | 1997-09-22 | Chemically induced stimulation of cleat formation in a subterranean coal formation |
US08/934,722 | 1997-09-22 |
Publications (2)
Publication Number | Publication Date |
---|---|
CA2247495A1 CA2247495A1 (en) | 1999-03-22 |
CA2247495C true CA2247495C (en) | 2009-03-17 |
Family
ID=25465961
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002247495A Expired - Fee Related CA2247495C (en) | 1997-09-22 | 1998-09-21 | Chemically induced stimulation of cleat formation in a subterranean coal formation |
Country Status (8)
Country | Link |
---|---|
US (1) | US5964290A (en) |
CN (1) | CN1117207C (en) |
CA (1) | CA2247495C (en) |
EA (1) | EA001524B1 (en) |
GB (1) | GB2329406B (en) |
PL (1) | PL188964B1 (en) |
UA (1) | UA52647C2 (en) |
ZA (1) | ZA988639B (en) |
Families Citing this family (24)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6431279B1 (en) * | 2000-07-14 | 2002-08-13 | Jacam Chemicals, L.L.C. | Process for in situ generation of chlorine dioxide in oil and gas well formations |
US7051809B2 (en) * | 2003-09-05 | 2006-05-30 | Conocophillips Company | Burn assisted fracturing of underground coal bed |
US20050082058A1 (en) * | 2003-09-23 | 2005-04-21 | Bustin Robert M. | Method for enhancing methane production from coal seams |
US7726399B2 (en) * | 2004-09-30 | 2010-06-01 | Bj Services Company | Method of enhancing hydraulic fracturing using ultra lightweight proppants |
CN100535384C (en) * | 2005-12-12 | 2009-09-02 | 中国矿业大学(北京) | Underground coal gasifier with air-lift point separating control and its process |
AU2008231767A1 (en) * | 2007-03-28 | 2008-10-02 | Shell Internationale Research Maatschappij B.V. | Method of interconnecting subterranean boreholes |
WO2010027455A1 (en) * | 2008-09-04 | 2010-03-11 | Ciris Energy, Inc. | Solubilization of algae and algal materials |
WO2011075163A1 (en) | 2009-12-18 | 2011-06-23 | Ciris Energy, Inc. | Biogasification of coal to methane and other useful products |
CN102168544B (en) * | 2011-03-28 | 2014-04-16 | 河南理工大学 | Method for surface modification and transmission increase of coal reservoirs by using chlorine dioxide |
CN102287176B (en) * | 2011-05-09 | 2014-12-10 | 河南理工大学 | Coal bed pressing crack liquid method |
HUE040215T2 (en) | 2012-06-26 | 2019-02-28 | Baker Hughes A Ge Co Llc | Methods of improving hydraulic fracture network |
US11111766B2 (en) | 2012-06-26 | 2021-09-07 | Baker Hughes Holdings Llc | Methods of improving hydraulic fracture network |
US10988678B2 (en) | 2012-06-26 | 2021-04-27 | Baker Hughes, A Ge Company, Llc | Well treatment operations using diverting system |
CN102953752B (en) * | 2012-10-30 | 2015-06-17 | 中国矿业大学 | Sealing method of water-containing drill hole for gas extraction |
CN102900396B (en) * | 2012-11-01 | 2014-12-10 | 中国矿业大学 | Method for integrally sealing and separating gas extraction drilled hole in coal seam |
CN103061734B (en) * | 2013-01-06 | 2016-04-20 | 山西蓝焰煤层气集团有限责任公司 | A kind of coal bed gas well bore hole chemistry makes cave method |
US9238587B2 (en) | 2013-03-15 | 2016-01-19 | Sabre Intellectual Property Holdings Llc | Method and system for the treatment of water and fluids with chlorine dioxide |
US10442711B2 (en) | 2013-03-15 | 2019-10-15 | Sabre Intellectual Property Holdings Llc | Method and system for the treatment of produced water and fluids with chlorine dioxide for reuse |
US8789592B2 (en) | 2013-04-24 | 2014-07-29 | Sabre Intellectual Property Holdings Llc | Flooding operations employing chlorine dioxide |
CN103396777A (en) * | 2013-07-22 | 2013-11-20 | 郝占元 | Application of chlorine dioxide blocking remover in coal bed modification |
US9920608B2 (en) | 2013-08-13 | 2018-03-20 | Board Of Regents, The University Of Texas System | Method of improving hydraulic fracturing by decreasing formation temperature |
CN110259427B (en) * | 2019-07-10 | 2023-05-26 | 河南理工大学 | Hydraulic fracturing fluid, gas extraction system and gas extraction method |
CN113216962B (en) * | 2021-06-28 | 2023-11-17 | 河南理工大学 | Synergistic anti-reflection desorption promotion experimental system and method for ultrasonic activated fracturing fluid |
CN114231322B (en) * | 2021-12-31 | 2023-04-28 | 北京派创石油技术服务有限公司 | Gas purifying and carbon dioxide circulating treatment method |
Family Cites Families (42)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4032193A (en) * | 1974-03-28 | 1977-06-28 | Shell Oil Company | Coal disaggregation by basic aqueous solution for slurry recovery |
US4043395A (en) * | 1975-03-13 | 1977-08-23 | Continental Oil Company | Method for removing methane from coal |
GB1492238A (en) * | 1976-06-23 | 1977-11-16 | Moskov Gor Inst | Method for reducing gas and dust emission from a coal sea |
NL7800005A (en) * | 1978-01-02 | 1979-07-04 | Stamicarbon | PROCEDURE FOR GETTING METHANE IN SITU FROM GREAT DEPTH CARBON LAYERS. |
CA1140457A (en) * | 1979-10-19 | 1983-02-01 | Noval Technologies Ltd. | Method for recovering methane from coal seams |
US4368922A (en) * | 1980-12-02 | 1983-01-18 | W. R. Grace & Co. | Method for solution mining of complex carbonaceous materials |
US4391327A (en) * | 1981-05-11 | 1983-07-05 | Conoco Inc. | Solvent foam stimulation of coal degasification well |
US4424863A (en) * | 1981-10-06 | 1984-01-10 | Mobil Oil Corporation | Oil recovery by waterflooding |
US4537252A (en) * | 1982-04-23 | 1985-08-27 | Standard Oil Company (Indiana) | Method of underground conversion of coal |
US4662439A (en) * | 1984-01-20 | 1987-05-05 | Amoco Corporation | Method of underground conversion of coal |
US4591443A (en) * | 1984-11-08 | 1986-05-27 | Fmc Corporation | Method for decontaminating a permeable subterranean formation |
US4747642A (en) * | 1985-02-14 | 1988-05-31 | Amoco Corporation | Control of subsidence during underground gasification of coal |
US4662443A (en) * | 1985-12-05 | 1987-05-05 | Amoco Corporation | Combination air-blown and oxygen-blown underground coal gasification process |
DE3608109A1 (en) * | 1986-03-12 | 1987-09-17 | Diehl Gmbh & Co | BRAKE DEVICE FOR A SPIN-STABILIZED PROJECTILE |
US4765407A (en) * | 1986-08-28 | 1988-08-23 | Amoco Corporation | Method of producing gas condensate and other reservoirs |
US4756367A (en) * | 1987-04-28 | 1988-07-12 | Amoco Corporation | Method for producing natural gas from a coal seam |
SU1492238A1 (en) * | 1987-06-15 | 1989-07-07 | Харьковский Автомобильно-Дорожный Институт Им.Комсомола Украины | Method for evaluating physical and mechanical properties of materials |
US4833170A (en) * | 1988-02-05 | 1989-05-23 | Gtg, Inc. | Process and apparatus for the production of heavier hydrocarbons from gaseous light hydrocarbons |
US4973453A (en) * | 1988-02-05 | 1990-11-27 | Gtg, Inc. | Apparatus for the production of heavier hydrocarbons from gaseous light hydrocarbons |
US4883122A (en) * | 1988-09-27 | 1989-11-28 | Amoco Corporation | Method of coalbed methane production |
US4913237A (en) * | 1989-02-14 | 1990-04-03 | Amoco Corporation | Remedial treatment for coal degas wells |
US5048328A (en) * | 1989-02-24 | 1991-09-17 | Amoco Corporation | Method of determining the porosity and irreducible water saturation of a coal cleat system |
US4993491A (en) * | 1989-04-24 | 1991-02-19 | Amoco Corporation | Fracture stimulation of coal degasification wells |
SU1693265A1 (en) * | 1989-09-06 | 1991-11-23 | Московский Горный Институт | Method of hydraulic mining of coal bed |
US5014788A (en) * | 1990-04-20 | 1991-05-14 | Amoco Corporation | Method of increasing the permeability of a coal seam |
US5099921A (en) * | 1991-02-11 | 1992-03-31 | Amoco Corporation | Recovery of methane from solid carbonaceous subterranean formations |
US5085274A (en) * | 1991-02-11 | 1992-02-04 | Amoco Corporation | Recovery of methane from solid carbonaceous subterranean of formations |
US5133406A (en) * | 1991-07-05 | 1992-07-28 | Amoco Corporation | Generating oxygen-depleted air useful for increasing methane production |
US5332036A (en) * | 1992-05-15 | 1994-07-26 | The Boc Group, Inc. | Method of recovery of natural gases from underground coal formations |
US5265678A (en) * | 1992-06-10 | 1993-11-30 | Halliburton Company | Method for creating multiple radial fractures surrounding a wellbore |
US5388641A (en) * | 1993-11-03 | 1995-02-14 | Amoco Corporation | Method for reducing the inert gas fraction in methane-containing gaseous mixtures obtained from underground formations |
US5388645A (en) * | 1993-11-03 | 1995-02-14 | Amoco Corporation | Method for producing methane-containing gaseous mixtures |
US5388643A (en) * | 1993-11-03 | 1995-02-14 | Amoco Corporation | Coalbed methane recovery using pressure swing adsorption separation |
US5388640A (en) * | 1993-11-03 | 1995-02-14 | Amoco Corporation | Method for producing methane-containing gaseous mixtures |
US5566755A (en) * | 1993-11-03 | 1996-10-22 | Amoco Corporation | Method for recovering methane from a solid carbonaceous subterranean formation |
US5388642A (en) * | 1993-11-03 | 1995-02-14 | Amoco Corporation | Coalbed methane recovery using membrane separation of oxygen from air |
US5419396A (en) * | 1993-12-29 | 1995-05-30 | Amoco Corporation | Method for stimulating a coal seam to enhance the recovery of methane from the coal seam |
US5417286A (en) * | 1993-12-29 | 1995-05-23 | Amoco Corporation | Method for enhancing the recovery of methane from a solid carbonaceous subterranean formation |
US5439054A (en) * | 1994-04-01 | 1995-08-08 | Amoco Corporation | Method for treating a mixture of gaseous fluids within a solid carbonaceous subterranean formation |
US5669444A (en) * | 1996-01-31 | 1997-09-23 | Vastar Resources, Inc. | Chemically induced stimulation of coal cleat formation |
US5865248A (en) * | 1996-01-31 | 1999-02-02 | Vastar Resources, Inc. | Chemically induced permeability enhancement of subterranean coal formation |
US5769165A (en) * | 1996-01-31 | 1998-06-23 | Vastar Resources Inc. | Method for increasing methane recovery from a subterranean coal formation by injection of tail gas from a hydrocarbon synthesis process |
-
1997
- 1997-09-22 US US08/934,722 patent/US5964290A/en not_active Expired - Lifetime
-
1998
- 1998-09-03 GB GB9819229A patent/GB2329406B/en not_active Expired - Fee Related
- 1998-09-21 ZA ZA988639A patent/ZA988639B/en unknown
- 1998-09-21 PL PL98328756A patent/PL188964B1/en not_active IP Right Cessation
- 1998-09-21 EA EA199800749A patent/EA001524B1/en not_active IP Right Cessation
- 1998-09-21 CA CA002247495A patent/CA2247495C/en not_active Expired - Fee Related
- 1998-09-21 UA UA98094935A patent/UA52647C2/en unknown
- 1998-09-22 CN CN98120682A patent/CN1117207C/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
PL328756A1 (en) | 1999-03-29 |
PL188964B1 (en) | 2005-05-31 |
CA2247495A1 (en) | 1999-03-22 |
ZA988639B (en) | 1999-03-31 |
GB9819229D0 (en) | 1998-10-28 |
US5964290A (en) | 1999-10-12 |
CN1117207C (en) | 2003-08-06 |
GB2329406A (en) | 1999-03-24 |
EA199800749A3 (en) | 1999-12-29 |
EA001524B1 (en) | 2001-04-23 |
CN1221849A (en) | 1999-07-07 |
EA199800749A2 (en) | 1999-04-29 |
UA52647C2 (en) | 2003-01-15 |
GB2329406B (en) | 2002-02-27 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
CA2247495C (en) | Chemically induced stimulation of cleat formation in a subterranean coal formation | |
US5669444A (en) | Chemically induced stimulation of coal cleat formation | |
US5967233A (en) | Chemically induced stimulation of subterranean carbonaceous formations with aqueous oxidizing solutions | |
US7819191B2 (en) | Method of fracturing a coalbed gas reservoir | |
US5944104A (en) | Chemically induced stimulation of subterranean carbonaceous formations with gaseous oxidants | |
AU735679B2 (en) | Chemically induced permeability enhancement of subterranean coal formation | |
AU720919B2 (en) | Increasing the rate of production of methane from subterranean coal and carbonaceous formations | |
RU2095560C1 (en) | Method for treating down-hole zone of oil bed | |
US4842056A (en) | Process for metal plating cement in a perforated well | |
RU2109790C1 (en) | Method of secondarily opening productive formation | |
RU2209936C2 (en) | Method of thermochemical treatment of oil formation | |
SU1613611A1 (en) | Method of winning coal from gas-saturated seam | |
DE19842407B4 (en) | Chemically induced pacing in a subterranean coal formation |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
EEER | Examination request | ||
MKLA | Lapsed |
Effective date: 20160921 |